This application claims the priority of Korean Patent Application No. 2003-52078, filed on Jul. 28, 2003, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein in its entirety by reference.
1. Field of the Invention
The present invention relates to a turbine type electric fuel pump for an automobile, and more particularly, to a turbine type electric fuel pump for an automobile in which the shapes of an impeller and other parts are improved to reduce loss of pressure due to a collision flow in the fuel pump that is installed in a fuel tank of the automobile and deliver fuel to an engine by the rotation of the impeller.
2. Description of the Related Art
A fuel pump for sucking fuel from a fuel tank and delivering the fuel at pressure to a vaporizer or a fuel injector is one of important parts in an automobile. The fuel pump is classified as a mechanical type and an electric type according to the type of driving a pump mechanism. Among these, a turbine type electric fuel pump, which is a sort of the electric fuel pump, is most used recently and consists of a DC motor portion and a turbine type pump portion. When a DC motor rotates, an impeller is rotated to generate a lift force so that a difference in pressure is generated and fuel is sucked in the impeller. Then, the pressure of fuel increases by a vortex flow generated by the continuous rotation of the impeller so that the fuel is discharged out of the pump.
The impeller used in the conventional turbine type electric fuel pump can be classified as a peripheral type or a side channel type. The peripheral type impeller has a plurality of radial blades provided at an edge of the impeller. The side-channel type impeller has a side ring connecting end tips of the blades that is added to the peripheral type impeller.
Referring to FIGS. 1A through 1E, the structure and operation of a conventional side ring type turbine type electric fuel pump 1 for an automobile are described. FIG. 1A is a cross-sectional view of a conventional side ring type fuel pump. FIG. 1B is a perspective view of the fuel intake case of FIG. 1A. FIG. 1C is an exploded perspective view of a fuel intake case 21, an impeller 23, and a fuel discharge case 22. FIGS. 1D and 1E are cross-sectional views of the pump portion of FIG. 1A, which schematically show the flow of fluid in the pump case.
Referring to FIG. 1A, a turbine type electric fuel pump 1 for an automobile has a pump portion 2 and a motor portion 3 which are included in a casing 4. The motor portion 3 includes a rotor 32 rotatably supported by a drive shaft 37 in the casing 4, a permanent magnet 33 installed on an inner surface of the casing 4 to encompass the rotor 32 by being separated a predetermined gap from the rotor 32, a rectifier 34 protruding from an end portion of the rotor 32, and a brush 35 intermittently contacting the rectifier 34 to provide electricity from an electric socket 5d provided at a portion of a pump upper surface cover 5 to the rectifier 34.
The pump portion 2 includes the fuel intake case 21 sucking fuel in a lower end portion of the casing 4, the impeller 23, and a fuel discharge case 22. The impeller 23 includes a disc portion 231 that is thin, a plurality of blades 234 radially formed at an edge of the disc portion 231, and a ring portion 233 connecting the blades 234. The impeller 23 is inserted in a pumping chamber that is encompassed by a circular edge 22b protruding along the edge of the fuel discharge case 22, so that the ring portion 233 is in contact with an annular inner ledge 22f (refer to FIG. 1C). Blades chambers 253 and 254 are formed between the blades 234 of the impeller 23 (refer to FIGS. 1D and 1E).
The drive shaft 37 coupled to the center of the rotor 32 of the motor portion 3 penetrates shaft assembly portions 22b and 232 of the fuel discharge case 22 and the impeller 23 and is supported by a shaft support pin 21f inserted in a shaft support portion 21b of the fuel intake case 21. When electricity supplied to the electric socket 5d is supplied to the rectifier 34 via a brush 35, the rotor 32 rotates by an electromagnetic operation of the coil 32a and the permanent magnet 33. Accordingly, the impeller 23 connected by the rotor 32 and the drive shaft 37 are rotated.
Reference numeral 5b of FIG. 1A denotes a check valve including a check ball 5b′ and a spring 5b″. When an engine of a car stops, the check valve 5b prevents backflow of fuel and maintains a particular remaining pressure in a fuel pump so that the engine can be easily restarted. Reference numeral 5c denotes a relief value which operates a valve when the pressure of a fuel line increases abnormally so that the pressure in the fuel pump can be constantly maintained. Reference numerals 36a and 36b denote bearings supporting the drive shaft 37 at the front and back sides thereof.
Referring to FIGS. 1B and 1C, a fuel intake hole 21a and a fuel discharge hole 22a are formed in the fuel intake case 21 and the fuel discharge case 22, respectively, corresponding to positions where the blades 234 of the impeller 23 are formed. An inlet side ring type duct 22c and an outlet side ring type duct 22c are symmetrically formed at inner surfaces 21d and 22d of the fuel intake case 21 and the fuel discharge case 22, respectively. An end portion 22e of the outlet side ring type duct 22c is formed at the opposite side of the fuel intake hole 21a of the inlet side ring type duct 21c. An end portion 22e of the outlet side ring type duct 22c is formed at the opposite side of the fuel intake hole 21a of the inlet side ring type duct 21c. The fuel discharge hole 22a of the outlet side ring type duct 22c is formed at the opposite side of the end portion 21e of the inlet side ring type duct 21c. 
FIGS. 1D and 1E are sectional views of the pump portion 2 of FIG. 1A. In FIGS. 1D and 1E, the flow of fluid generated when fuel is sucked in through the fuel intake hole 21a by rotation of the impeller 23 and discharged through the fuel discharge hole 22a after circulating within the pump is schematically illustrated.
Semicircular sectional portions of the inlet side ring type duct 21c and the outlet side ring type duct 22c form an inlet side transfer chamber 251 and an outlet side transfer chamber 252, respectively. A space between the blades 234 of the impeller 23 is divided into two blade chambers 253 and 254 by a portion sharply protruding along a center line of an outer portion of the disc portion 231. The inlet side transfer chamber 251, the outlet side transfer chamber 252, the inlet side blade chamber 253, and the outlet side blade chamber 254 forms a connection path 25 connecting the fuel intake hole 21a and the fuel discharge hole 22a. After entering through the fuel intake hole 21a, the fuel circulates around the impeller 23 along the connection path 25 and forms circular vortex flows VF each rotating in the opposite direction in the connection path 25. A portion of the vortex flow of the inlet side transfer chamber 251 and the inlet side blade chamber 253 are moved to the vortex flow in the outlet side transfer chamber 252 and the outlet side blade chamber 254.
However, since the inner circumferential surface of the ring portion 233 of the impeller 23 shown in FIG. 1D, is flat, a collision flow CF which collides against the rotation direction of the fluid in the blade chambers 253 and 254 exists so that loss of pressure in the pump occurs. To reduce the counter flow of the fluid in the pump, a structure of the impeller 23 as shown in FIG. 1E, in which a round shape is applied to the inner circumferential surface of the ring portion 233 of the impeller 23 such that the inner circumferential surface protrudes inwardly in a radial direction of the impeller 23 from both upper and lower ends to a center line CL, has been suggested. However, in the case of the impeller 23 of FIG. 1E, although the collision flow directly colliding against the inner circumferential surface of the ring portion 233 may decrease, loss of pressure occurs due to the collision flow CF generated when two vortex flows VF collide at the center line CL.
As a result, when the loss of pressure is generated due to the collision between the fluids, the fluid amount performance and efficiency of the pump is deteriorated so that fuel cannot be sufficiently supplied to an engine. When the initial rotation number of a fuel pump is set to be high in consideration of the pressure loss at the stage of designing a car, noise and vibration due to the operation of the fuel pump increase. Thus, passengers desiring quite driving is inconvenienced by the noise and vibration. Furthermore, the life span of the fuel pump is reduced.